Quantum dot light-emitting device

ABSTRACT

A quantum dot light-emitting device includes: a first electrode; a second electrode opposite to the first electrode; an emission layer between the first electrode and the second electrode, the emission layer including quantum dots; and an inorganic layer between the emission layer and the second electrode, the inorganic layer including a metal halide.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/362,388, filed Mar. 22, 2019, which is a continuation of U.S. patentapplication Ser. No. 15/953,344, filed Apr. 13, 2018, now U.S. Pat. No.10,283,672, which is a continuation of U.S. patent application Ser. No.15/264,422, filed Sep. 13, 2016, now U.S. Pat. No. 9,947,828, whichclaims priority to and the benefit of Korean Patent Application No.10-2016-0032073, filed Mar. 17, 2016, the entire content of each ofwhich is incorporated herein by reference.

BACKGROUND 1. Field

One or more embodiments of the present disclosure relate to a quantumdot light-emitting device.

2. Description of the Related Art

A quantum dot light-emitting device is a light-emitting device includingquantum dots as an emission layer thereof.

Quantum dots include nano crystals of semiconductor material that have aquantum confinement effect. By being excited to an energy excitationstate by light emitted from an excitation source, quantum dotsspontaneously emit energy having a corresponding energy band gap.Quantum dots of the same material may emit light having differentwavelengths depending on the size of the quantum dots. Accordingly, byadjusting the size of quantum dots, light having a desired wavelengthrange may be obtained, and devices having improved characteristics incolor purity and luminance efficiency may be obtained. Therefore,quantum dots are applicable to various devices.

SUMMARY

One or more embodiments of the present disclosure include a quantum dotlight-emitting device having long lifespan, high reliability and highreproducibility.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

According to one or more embodiments, a light-emitting device includes:a first electrode; a second electrode opposite to the first electrode;an emission layer between the first electrode and the second electrode,the emission layer including quantum dots; and an inorganic layerbetween the emission layer and the second electrode, the inorganic layerincluding a metal halide.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of embodiments, taken inconjunction with the accompanying drawings in which:

FIG. 1 is a schematic cross-sectional view of a light-emitting deviceaccording to an embodiment of the present disclosure; and

FIG. 2 is a schematic cross-sectional view of a light-emitting deviceaccording to another embodiment of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in more detail to embodiments, examples ofwhich are illustrated in the accompanying drawings, wherein likereference numerals refer to like elements throughout. In this regard,the present embodiments may have different forms and should not beconstrued as being limited to the description set forth herein.Accordingly, the embodiments are merely described below, by referring tothe figures, to explain aspects of embodiments of the presentdescription. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items. Expressionssuch as “at least one of,” when preceding a list of elements, modify theentire list of elements and do not modify the individual elements of thelist.

According to an embodiment of the present disclosure, a light-emittingdevice includes: a first electrode; a second electrode opposite to(e.g., facing) the first electrode; an emission layer between the firstelectrode and the second electrode and including quantum dots; and aninorganic layer between the emission layer and the second electrode andincluding a metal halide.

In some embodiments, the metal halide may include an alkaline metalhalide, an alkaline earth metal halide, a transition metal halide, apost-transition metal halide, or any combination thereof. As usedherein, the terms “combination thereof” and “combinations thereof” mayrefer to a chemical combination (e.g., an alloy or chemical compound), amixture, or a laminated structure of components.

For example, the metal halide may include a transition metal halide.

In some embodiments, the metal halide may include a silver (Ag) halide,a cadmium (Cd) halide, a mercury (Hg) halide, a manganese (Mn) halide,an iron (Fe) halide, a cobalt (Co) halide, a nickel (Ni) halide, acopper (Cu) halide, a zinc (Zn) halide, or any combination thereof.However, the present disclosure is not limited thereto.

In some embodiments, the metal halide may be a transition metalfluoride.

For example, the metal halide may include an Ag fluoride, a Cd fluoride,a Hg fluoride, a Mn fluoride, a Fe fluoride, a Co fluoride, a Nifluoride, a Cu fluoride, a Zn fluoride, or any combination thereof.However, the present disclosure is not limited thereto.

In some other embodiments, the metal halide may include AgF, AgF₂, CdF₂,HgF₂, MnF₂, FeF₂, CoF₂, NiF₂, CuF, CuF₂, ZnF₂, or any combinationthereof. However, the present disclosure is not limited thereto.

For example, the metal halide may include FeF₂. However, the presentdisclosure is not limited thereto.

In some embodiments, the metal halide may consist of AgF, AgF₂, CdF₂,HgF₂, MnF₂, FeF₂, CoF₂, NiF₂, CuF, CuF₂, ZnF₂, or any combinationthereof. However, the present disclosure is not limited thereto.

For example, the metal halide may consist of FeF₂.

In some other embodiments, the inorganic layer may further include atrivalent metal ion.

For example, the inorganic layer may further include at least one metalion selected from Al³⁺, Ga³⁺, and In³⁺. However, the present disclosureis not limited thereto.

In some other embodiments, the trivalent metal ion may be doped with ametal halide as listed above. However, the present disclosure is notlimited thereto.

In some embodiments, the metal halide may have an energy band gap ofabout 3.1 eV to about 4.6 eV. For example, the metal halide may have anenergy band gap of about 3.2 eV to about 3.8 eV. However, the presentdisclosure is not limited thereto.

In some other embodiments, the metal halide may have a melting point ofabout 700° C. to about 1400° C. For example, the metal halide may have amelting point of about 800° C. to 1200° C. However, the presentdisclosure is not limited thereto.

In some embodiments, the inorganic layer may directly contact(physically contact) the emission layer.

For example, the inorganic layer may have a thickness of about 200 Å toabout 1000 Å, and in some embodiments, about 300 Å to about 500 Å.However, the present disclosure is not limited thereto.

In some other embodiments, the quantum dots may have a core-shellstructure including a core including a first semiconductor crystal and ashell including a second semiconductor crystal. In some embodiments, thefirst semiconductor crystal and the second semiconductor crystal may bedifferent from one another.

For example, a first semiconductor of the first semiconductor crystaland a second conductor of the second semiconductor crystal may eachindependently include a compound including a Group 12 element and aGroup 16 element, a compound including a Group 13 element and a Group 15element, a compound including a Group 14 element and a Group 16 element,or any combination thereof.

For example, the first semiconductor and the second semiconductor mayeach independently include CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, HgS, HgSe,HgTe, CdSTe, GaP, GaAs, GaSb, InP, InAs, InSb, PbS, PbSe, PbTe, or anycombination thereof. However, the present disclosure is not limitedthereto.

For example, the first semiconductor may include CdSe, CdTe, ZnSe, InPInAs, PbS, PbSe, PbTe, or any combination thereof. The secondsemiconductor may include ZnSe, ZnS, CdS, HgS, GaAs, or any combinationthereof. However, the present disclosure is not limited thereto.

In some embodiments, the second semiconductor may have an energy bandgap that is equal to or larger than the energy band gap of the firstsemiconductor. However, the present disclosure is not limited thereto.

For example, the light-emitting device may further include a substrateunder the first electrode. The first electrode may be an anode, and thesecond electrode may be a cathode. A hole transport region may bebetween the first electrode and the emission layer, and an electrontransport region may be between the second electrode and the emissionlayer. The inorganic layer may be in the electron transport region.

For example, the light-emitting device may further include a substrateunder the first electrode. The first electrode may be a cathode, and thesecond electrode may be an anode. An electron transport region may bebetween the first electrode and the emission layer, and a hole transportregion may be between the second electrode and the emission layer. Theinorganic layer may be in the electron transport region.

In some embodiments, the hole transport region may include at least onelayer selected from a hole injection layer, a hole transport layer, anemission auxiliary layer, and electron blocking layer. However, thepresent disclosure is not limited thereto.

When the inorganic layer is formed using another material such as ZnO bya solution process (e.g., spin coating, inkjet printing, or the like),the inorganic layer may undergo stability degradation over time, leadingto reduced device reproducibility in manufacturing processes. Inaddition, oxygen outgassing caused from the thermal decomposition of ZnOmay lower a level of vacuum (e.g., of a level of vacuum of a processchamber for manufacturing the device) and hinder deposition.

However, in the light-emitting device according to any of theembodiments of the present disclosure, the emission layer may includequantum dots and the inorganic layer may include a metal halide, whereinthe energy level of the metal halide is appropriate or suitable for theemission layer including quantum dots and the melting point thereof isalso low to facilitate thermal deposition. Accordingly, it may be easierto ensure reliability and reproducibility of devices according toembodiments of the present disclosure, as compared to a light-emittingdevice including an inorganic layer using another material (e.g., ZnO).

When the metal halide is doped with a trivalent metal ion, the energylevel of the metal halide may be adjusted to be appropriate or suitablefor the emission layer including quantum dots, so that a light-emittingdevice having a long lifespan, high reliability, and highreproducibility may be provided.

Description of FIG. 1

FIG. 1 is a schematic cross-sectional view of a light-emitting device 20according to an exemplary embodiment of the present disclosure. Thelight-emitting device 20 may include a first electrode 21, a holetransport region 22, an emission layer 23 including quantum dots 25, anelectron transport region 26, and a second electrode 27.

For example, the first electrode 21 of the light-emitting device 20 ofFIG. 1 may be an anode, and the second electrode 27 may be a cathode.

Description of FIG. 2

FIG. 2 is a schematic cross-sectional view of a light-emitting device 30according to an exemplary embodiment of the present disclosure. Thelight-emitting device 30 may include a first electrode 21, an electrontransport region 26, an emission layer 23 including quantum dots 25, ahole transport region 22, and a second electrode 27.

For example, the first electrode 21 of the light-emitting device 30 ofFIG. 2 may be a cathode, and the second electrode 27 may be an anode.

Hereinafter, structures of the light-emitting devices 20 and 30according to embodiments of the disclosure and a method of manufacturingthe same will now be described with reference to FIGS. 1 and 2.

First Electrode 21

A substrate may be further disposed under the first electrode 21 or onthe second electrode 27. The substrate may be a glass substrate or atransparent plastic substrate having strong mechanical strength, thermalstability, transparency, surface smoothness, ease of handling, and waterresistance.

The first electrode 21 may be formed by depositing or sputtering a firstelectrode-forming material on the substrate. When the first electrode 21is an anode, a material having a high work function may be selected as amaterial of the first electrode 21 to facilitate hole injection. Whenthe first electrode 21 is a cathode, a material of the first electrode21 may be a metal having a low work function, an alloy, an electricallyconductive compound, or any combination thereof.

The first electrode 21 may be a reflective electrode, asemi-transmissive electrode, or a transmissive electrode. To form atransmissive electrode as the first electrode 21, a material of thefirst electrode 21 may be selected from indium tin oxide (ITO), indiumzinc oxide (IZO), tin oxide (SnO₂), zinc oxide (ZnO), zinc tin oxide(ZTO), copper indium oxide (CIO), copper zinc oxide (CZO), gallium zincoxide (GZO), aluminum zinc oxide (AZO), and any combinations thereof.However, the present disclosure is not limited thereto. In some otherembodiments, to form a semi-transmissive electrode or reflectiveelectrode as the first electrode 21, a material of the first electrode21 may be selected from magnesium (Mg), lithium (Li), silver (Ag),aluminum (Al), aluminum-lithium (Al—Li), calcium (Ca), magnesium-indium(Mg—In), magnesium-silver (Mg—Ag), ytterbium (Yb), and any combinationsthereof. However, the present disclosure is not limited thereto. In someother embodiments, a material of the first electrode 21 may includegraphene, carbon nanotube, or a conductive polymer such aspoly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS).However, the present disclosure is not limited thereto.

The first electrode 21 may have a single-layer structure or amulti-layer structure including a plurality of layers. For example, thefirst electrode 21 may have, but is not limited to, a three-layeredstructure including ITO, Ag, and ITO layers. However, the presentdisclosure is not limited thereto.

Hole Transport Region 22

The hole transport region 22 may have i) a single-layer structureincluding a single layer including a single material, ii) a single-layerstructure including a single layer including a plurality of differentmaterials, or iii) a multi-layer structure including a plurality oflayers including different materials.

The hole transport region 22 may include at least one layer selectedfrom a hole injection layer, a hole transport layer, an emissionauxiliary layer, and an electron blocking layer.

For example, the hole transport region 22 may have a single-layerstructure including a single layer including a plurality of differentmaterials, or a multi-layer structure in which the following layers aresequentially stacked upon one another, e.g., hole injection layer/holetransport layer, hole injection layer/hole transport layer/emissionauxiliary layer, hole injection layer/emission auxiliary layer, holetransport layer/emission auxiliary layer, or hole injection layer/holetransport layer/electron blocking layer. However, the present disclosureis not limited thereto.

The hole transport region 22 may include at least one selected fromm-MTDATA, TDATA, 2-TNATA, NPB(NPD), β-NPB, TPD, Spiro-TPD, Spiro-NPB,methylated NPB, TAPC, HMTPD, 4,4′,4″-tris(N-carbazolyl)triphenylamine(TCTA), polyaniline/dodecylbenzene sulfonic acid (Pani/DBSA),poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS),polyaniline/camphor sulfonic acid (Pani/CSA), polyaniline/poly(4-styrenesulfonate) (PANI/PSS), a compound represented by Formula 201, and acompound represented by Formula 202.

In Formulae 201 and 202,

L₂₀₁ to L₂₀₄ may be each independently selected from a substituted orunsubstituted C₃-C₁₀ cycloalkylene group, a substituted or unsubstitutedC₁-C₁₀ heterocycloalkylene group, a substituted or unsubstituted C₃-C₁₀cycloalkenylene group, a substituted or unsubstituted C₁-C₁₀heterocycloalkenylene group, a substituted or unsubstituted C₆-C₆₀arylene group, a substituted or unsubstituted C₁-C₆₀ heteroarylenegroup, a substituted or unsubstituted divalent non-aromatic condensedpolycyclic group, and a substituted or unsubstituted divalentnon-aromatic condensed heteropolycyclic group;

L₂₀₅ may be selected from *—O—*′, *—N(Q₂₀₁)-*′, a substituted orunsubstituted C₁-C₂₀ alkylene group, a substituted or unsubstitutedC₂-C₂₀ alkenylene group, a substituted or unsubstituted C₃-C₁₀cycloalkylene group, a substituted or unsubstituted C₁-C₁₀heterocycloalkylene group, a substituted or unsubstituted C₃-C₁₀cycloalkenylene group, a substituted or unsubstituted C₁-C₁₀heterocycloalkenylene group, a substituted or unsubstituted C₆-C₆₀arylene group, a substituted or unsubstituted C₁-C₆₀ heteroarylenegroup, a substituted or unsubstituted divalent non-aromatic condensedpolycyclic group, and a substituted or unsubstituted divalentnon-aromatic condensed heteropolycyclic group;

xa1 to xa4 may be each independently an integer selected from 0 to 3;

xa5 may be an integer selected from 1 to 10; and

R₂₀₁ to R₂₀₄ and Q₂₀₁ may be each independently selected from asubstituted or unsubstituted C₃-C₁₀ cycloalkyl group, a substituted orunsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted orunsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or unsubstitutedC₁-C₁₀ heterocycloalkenyl group, a substituted or unsubstituted C₆-C₆₀aryl group, a substituted or unsubstituted C₆-C₆₀ aryloxy group, asubstituted or unsubstituted C₆-C₆₀ arylthio group, a substituted orunsubstituted C₁-C₆₀ heteroaryl group, a substituted or unsubstitutedmonovalent non-aromatic condensed polycyclic group, and a substituted orunsubstituted monovalent non-aromatic condensed heteropolycyclic group.

For example, in Formula 202, optionally, R₂₀₁ and R₂₀₂ may be linked toeach other via a single bond, a dimethyl-methylene group, or adiphenyl-methylene group. Optionally, R₂₀₃ and R₂₀₄ may be linked toeach other via a single bond, a dimethyl-methylene group, or adiphenyl-methylene group.

In some embodiments, in Formulae 201 and 202,

L₂₀₁ to L₂₀₅ may be each independently selected from:

a phenylene group, a pentalenylene group, an indenylene group, anaphthylene group, an azulenylene group, a heptalenylene group, anindacenylene group, an acenaphthylene group, a fluorenylene group, aspiro-bifluorenylene group, a benzofluorenylene group, adibenzofluorenylene group, a phenalenylene group, a phenanthrenylenegroup, an anthracenylene group, a fluoranthenylene group, atriphenylenylene group, a pyrenylene group, a chrysenylene group, anaphthacenylene group, a picenylene group, a perylenylene group, apentaphenylene group, a hexacenylene group, a pentacenylene group, arubicenylene group, a coronenylene group, an ovalenylene group, athiophenylene group, a furanylene group, a carbazolylene group, anindolylene group, an isoindolylene group, a benzofuranylene group, abenzothiophenylene group, a dibenzofuranylene group, adibenzothiophenylene group, a benzocarbazolylene group, adibenzocarbazolylene group, a dibenzosilolylene group, and apyridinylene group, and

a phenylene group, a pentalenylene group, an indenylene group, anaphthylene group, an azulenylene group, a heptalenylene group, anindacenylene group, an acenaphthylene group, a fluorenylene group, aspiro-bifluorenylene group, a benzofluorenylene group, adibenzofluorenylene group, a phenalenylene group, a phenanthrenylenegroup, an anthracenylene group, a fluoranthenylene group, atriphenylenylene group, a pyrenylene group, a chrysenylene group, anaphthacenylene group, a picenylene group, a perylenylene group, apentaphenylene group, a hexacenylene group, a pentacenylene group, arubicenylene group, a coronenylene group, an ovalenylene group, athiophenylene group, a furanylene group, a carbazolylene group, anindolylene group, an isoindolylene group, a benzofuranylene group, abenzothiophenylene group, a dibenzofuranylene group, adibenzothiophenylene group, a benzocarbazolylene group, adibenzocarbazolylene group, a dibenzosilolylene group, and apyridinylene group, each substituted with at least one selected fromdeuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitrogroup, an amidino group, a hydrazino group, a hydrazono group, a C₁-C₂₀alkyl group, a C₁-C₂₀ alkoxy group, a cyclopentyl group, a cyclohexylgroup, a cycloheptyl group, a cyclopentenyl group, a cyclohexenyl group,a phenyl group, a biphenyl group, a terphenyl group, a phenyl groupsubstituted with a C₁-C₁₀ alkyl group, a phenyl group substituted with—F, a pentalenyl group, an indenyl group, a naphthyl group, an azulenylgroup, a heptalenyl group, an indacenyl group, an acenaphthyl group, afluorenyl group, a spiro-bifluorenyl group, a benzofluorenyl group, adibenzofluorenyl group, a phenalenyl group, a phenanthrenyl group, ananthracenyl group, a fluoranthenyl group, a triphenylenyl group, apyrenyl group, a chrysenyl group, a naphthacenyl group, a picenyl group,a perylenyl group, a pentaphenyl group, a hexacenyl group, a pentacenylgroup, a rubicenyl group, a coronenyl group, an ovalenyl group, athiophenyl group, a furanyl group, a carbazolyl group, an indolyl group,an isoindolyl group, a benzofuranyl group, a benzothiophenyl group, adibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolylgroup, a dibenzocarbazolyl group, a dibenzosilolyl group, a pyridinylgroup, —Si(Q₃₁)(Q₃₂)(Q₃₃), and —N(Q₃₁)(Q₃₂),

wherein Q₃₁ to Q₃₃ may be each independently selected from a C₁-C₁₀alkyl group, a C₁-C₁₀ alkoxy group, a phenyl group, a biphenyl group, aterphenyl group and a naphthyl group.

In some other embodiments, xa1 to xa4 may be each independently 0, 1 or2.

In some other embodiments, xa5 may be 1, 2, 3, or 4.

In some other embodiments, R₂₀₁ to R₂₀₄ and Q₂₀₁ may be eachindependently selected from a phenyl group, a biphenyl group, aterphenyl group, a pentalenyl group, an indenyl group, a naphthyl group,an azulenyl group, a heptalenyl group, an indacenyl group, anacenaphthyl group, a fluorenyl group, a spiro-bifluorenyl group, abenzofluorenyl group, a dibenzofluorenyl group, a phenalenyl group, aphenanthrenyl group, an anthracenyl group, a fluoranthenyl group, atriphenylenyl group, a pyrenyl group, a chrysenyl group, a naphthacenylgroup, a picenyl group, a perylenyl group, a pentaphenyl group, ahexacenyl group, a pentacenyl group, a rubicenyl group, a coronenylgroup, an ovalenyl group, a thiophenyl group, a furanyl group, acarbazolyl group, an indolyl group, an isoindolyl group, a benzofuranylgroup, a benzothiophenyl group, a dibenzofuranyl group, adibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolylgroup, a dibenzosilolyl group and a pyridinyl group, and

a phenyl group, a biphenyl group, a terphenyl group, a pentalenyl group,an indenyl group, a naphthyl group, an azulenyl group, a heptalenylgroup, an indacenyl group, an acenaphthyl group, a fluorenyl group, aspiro-bifluorenyl group, a benzofluorenyl group, a dibenzofluorenylgroup, a phenalenyl group, a phenanthrenyl group, an anthracenyl group,a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, achrysenyl group, a naphthacenyl group, a picenyl group, a perylenylgroup, a pentaphenyl group, a hexacenyl group, a pentacenyl group, arubicenyl group, a coronenyl group, an ovalenyl group, a thiophenylgroup, a furanyl group, a carbazolyl group, an indolyl group, anisoindolyl group, a benzofuranyl group, a benzothiophenyl group, adibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolylgroup, a dibenzocarbazolyl group, a dibenzosilolyl group, and apyridinyl group, each substituted with at least one selected fromdeuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitrogroup, an amidino group, a hydrazino group, a hydrazono group, a C₁-C₂₀alkyl group, a C₁-C₂₀ alkoxy group, a cyclopentyl group, a cyclohexylgroup, a cycloheptyl group, a cyclopentenyl group, a cyclohexenyl group,a phenyl group, a biphenyl group, a terphenyl group, a phenyl groupsubstituted with a C₁-C₁₀ alkyl group, a phenyl group substituted with—F, a pentalenyl group, an indenyl group, a naphthyl group, an azulenylgroup, a heptalenyl group, an indacenyl group, an acenaphthyl group, afluorenyl group, a spiro-bifluorenyl group, a benzofluorenyl group, adibenzofluorenyl group, a phenalenyl group, a phenanthrenyl group, ananthracenyl group, a fluoranthenyl group, a triphenylenyl group, apyrenyl group, a chrysenyl group, a naphthacenyl group, a picenyl group,a perylenyl group, a pentaphenyl group, a hexacenyl group, a pentacenylgroup, a rubicenyl group, a coronenyl group, an ovalenyl group, athiophenyl group, a furanyl group, a carbazolyl group, an indolyl group,an isoindolyl group, a benzofuranyl group, a benzothiophenyl group, adibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolylgroup, a dibenzocarbazolyl group, a dibenzosilolyl group, a pyridinylgroup, —Si(Q₃₁)(Q₃₂)(Q₃₃), and —N(Q₃₁)(Q₃₂),

wherein Q₃₁ to Q₃₃ may be defined as described above.

In some other embodiments, in Formula 201, at least one of R₂₀₁ to R₂₀₃may be each independently selected from:

a fluorenyl group, a spiro-bifluorenyl group, a carbazolyl group, adibenzofuranyl group, and a dibenzothiophenyl group, and

a fluorenyl group, a spiro-bifluorenyl group, a carbazolyl group, adibenzofuranyl group and a dibenzothiophenyl group, each substitutedwith at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxylgroup, a cyano group, a nitro group, an amidino group, a hydrazinogroup, a hydrazono group, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, acyclopentyl group, a cyclohexyl group, a cycloheptyl group, acyclopentenyl group, a cyclohexenyl group, a phenyl group, a biphenylgroup, a terphenyl group, a phenyl group substituted with a C₁-C₁₀ alkylgroup, a phenyl group substituted with —F, a naphthyl group, a fluorenylgroup, a spiro-bifluorenyl group, a carbazolyl group, a dibenzofuranylgroup, and a dibenzothiophenyl group. However, the present disclosure isnot limited thereto.

In some other embodiments, in Formula 202, i) R₂₀₁ and R₂₀₂ may belinked to each other via a single bond, and/or ii) R₂₀₃ and R₂₀₄ may belinked to each other via a single bond.

In some other embodiments, in Formula 202, at least one of R₂₀₁ to R₂₀₄may be selected from:

a carbazolyl group, and

a carbazolyl group substituted with at least one selected fromdeuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitrogroup, an amidino group, a hydrazino group, a hydrazono group, a C₁-C₂₀alkyl group, a C₁-C₂₀ alkoxy group, a cyclopentyl group, a cyclohexylgroup, a cycloheptyl group, a cyclopentenyl group, a cyclohexenyl group,a phenyl group, a biphenyl group, a terphenyl group, a phenyl groupsubstituted with a C₁-C₁₀ alkyl group, a phenyl group substituted with—F, a naphthyl group, a fluorenyl group, a spiro-bifluorenyl group, acarbazolyl group, a dibenzofuranyl group, and a dibenzothiophenyl group.However, the present disclosure is not limited thereto.

The hole transport region 22 may include metal oxide nanoparticles. Themetal oxide nanoparticles may include at least one selected from NiO,MoO₃, Cr₂O₃, Bi₂O₃, a p-type ZnO, and a p-type GaN.

The hole transport region 22 may have a thickness of about 100 Å toabout 10000 Å, for example, about 100 Å to about 1000 Å. The holetransport region 22 may include at least one selected from a holeinjection layer and a hole transport layer. When the hole transportregion 22 includes at least one selected from a hole injection layer anda hole transport layer, the hole injection layer may have a thickness ofabout 100 Å to about 9000 Å, for example, about 100 Å to about 1000 Å,and the hole transport layer may have a thickness of about 50 Å to about2000 Å, for example, about 100 Å to about 1500 Å. When the thicknessesof the hole transport region 22, the hole injection layer, and the holetransport layer are within these ranges, satisfactory or suitable holetransport characteristics may be obtained without a substantial increasein driving voltage.

The emission auxiliary layer may compensate for an optical resonancedistance of light according to a wavelength of the light emitted fromthe emission layer and thus may improve light-emission efficiency. Theelectron blocking layer may prevent or reduce electron injection fromthe electron transport region. The emission auxiliary layer and theelectron blocking layer may include materials of the hole transportregion 22 as described above.

p-Dopant

The hole transport region 22 may further include a charge-generatingmaterial to improve conductivity, in addition to the above-describedmaterials. The charge-generating material may be homogeneously ornon-homogeneously (e.g., heterogeneously) dispersed in the holetransport region 22.

The charge-generating material may be, for example, a p-dopant.

In some embodiments, the p-dopant may have a lowest unoccupied molecularorbital (LUMO) energy level of about −3.5 eV or less.

The p-dopant may include at least one selected from quinine derivatives,metal oxides, and cyano group-containing compounds. However, the presentdisclosure is not limited thereto.

For example, the p-dopant may include at least one selected from quinonederivatives such as tetracyanoquinonedimethane (TCNQ),2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), and/orthe like; metal oxides such as tungsten oxide, molybdenum oxide, and/orthe like; 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN);and a compound represented by Formula 221. However, the presentdisclosure is not limited thereto.

In Formula 221,

R₂₂₁ to R₂₂₃ may be each independently selected from a substituted orunsubstituted C₃-C₁₀ cycloalkyl group, a substituted or unsubstitutedC₁-C₁₀ heterocycloalkyl group, a substituted or unsubstituted C₃-C₁₀cycloalkenyl group, a substituted or unsubstituted C₁-C₁₀heterocycloalkenyl group, a substituted or unsubstituted C₆-C₆₀ arylgroup, a substituted or unsubstituted C₁-C₆₀ heteroaryl group, asubstituted or unsubstituted monovalent non-aromatic condensedpolycyclic group, and a substituted or unsubstituted monovalentnon-aromatic condensed heteropolycyclic group, wherein at least one ofR₂₂₁ to R₂₂₃ may have at least one substituent selected from a cyanogroup, —F, —Cl, —Br, —I, a C₁-C₂₀ alkyl group substituted with —F, aC₁-C₂₀ alkyl group substituted with —Cl, a C₁-C₂₀ alkyl groupsubstituted with —Br, and a C₁-C₂₀ alkyl group substituted with —I.

Emission Layer 23

The emission layer 23 may include quantum dots 25. The quantum dots 25,as a spherical (e.g., substantially spherical) semiconductornanomaterial having a size of about several nanometers (nm) to severalhundred nanometers, may include a core including a material having asmall band gap, and a shell surrounding the core.

The quantum dots 25 may have a core-shell structure including a coreincluding a first semiconductor crystal and a shell including a secondsemiconductor crystal. The first semiconductor and the secondsemiconductor are described above, and thus, further detaileddescription thereof will not be provided here.

Quantum dots are dispersed in coordinated form in a dispersion mediumsuch as an organic solvent or polymer resin. The dispersion medium maybe any suitable transparent medium that does not substantially affectthe wavelength conversion ability of quantum dots and does notsubstantially reflect or absorb light.

For example, the organic solvent may be at least one selected fromtoluene, chloroform, and ethanol. The polymer resin may include at leastone selected from epoxy, silicone, polyethylene, polystyrene, andacrylate.

Due to a quantum confinement effect, quantum dots may have discontinuousband gap energy, unlike a bulk state material. Quantum dots may have anenergy band gap that may vary depending on the size of quantum dots.Quantum dots of the same material but having different sizes may emitlight having different wavelengths. The smaller the size of a quantumdot, the higher the band gap energy and the shorter the wavelength oflight emitted from the quantum dot. Based on these characteristics ofquantum dots, the condition for growing quantum dots into nanocrystalsmay be appropriately or suitably varied to obtain light having a desiredwavelength range. Thus, by introducing such a quantum dot into alight-emitting device, it is possible to implement a light-emittingdevice having high luminance efficiency and color purity.

Electron Transport Region 26

The electron transport region 26 may include an inorganic layer. Forexample, the inorganic layer may directly contact the emission layer 23.The inorganic layer may include a metal halide. The inorganic layer andthe metal halide are described above, and a further detailed descriptionthereof will not be provided here.

In some embodiments, the electron transport region 26 may have i) asingle-layer structure including a single layer including a singlematerial, ii) a single-layer structure including a single layerincluding a plurality of different materials, or iii) a multi-layerstructure including a plurality of layers including different materials

The electron transport region 26 may include at least one layer selectedfrom a buffer layer, a hole blocking layer, an electron control layer,an electron transport layer, and an electron injection layer. However,the present disclosure is not limited thereto.

For example, the electron transport region 26 may have a structure ofelectron transport layer/electron injection layer, a structure of holeblocking layer/electron transport layer/electron injection layer, astructure of electron control layer/electron transport layer/electroninjection layer, or a structure of buffer layer/electron transportlayer/electron injection layer, wherein the layers of each structure aresequentially stacked from the emission layer 23 in the stated order.However, the present disclosure is not limited thereto.

The electron transport region 26 (for example, the buffer layer, thehole blocking layer, the electron control layer, or the electrontransport layer in the emission transport region 26) may include ametal-free compound having at least one π electron-depletednitrogen-containing ring.

The “π electron-depleted nitrogen-containing ring,” as a ring-formingmoiety, may refer to a C₁-C₆₀ heterocyclic group having at least one*—N═*′ moiety.

For example, the “π electron-depleted nitrogen-containing ring” mayinclude i) a 5-membered to 7-membered heteromonocyclic group having atleast one *—N=*′ moiety, ii) a heteropolycyclic group including at leasttwo 5-membered to 7-membered heteromonocyclic groups having at least one*—N=*′ moiety that are condensed to one another (e.g., fused together),or iii) a heteropolycyclic group including at least one 5-membered to7-membered heteromonocyclic group having at least one *—N=*′ moiety andat least one C₅-C₆₀ carbocyclic group that are condensed to one another(e.g., fused together).

Examples of the π electron-depleted nitrogen-containing ring include animidazole, a pyrazole, a thiazole, an isothiazole, an oxazole, anisoxazole, a pyridine, a pyrazine, a pyrimidine, a pyridazine, anindazole, a purine, a quinoline, an isoquinoline, a benzoquinoline, aphthalazine, a naphthyridine, a quinoxaline, a quinazoline, a cinnoline,a phenanthridine, an acridine, a phenanthroline, a phenazine, abenzimidazole, an isobenzothiazole, a benzoxazole, an isobenzoxazole, atriazole, a tetrazole, an oxadiazole, a triazine, a thiadiazole, animidazopyridine, an imidazopyrimidine, and an azacarbazole. However, thepresent disclosure is not limited thereto.

For example, the electron transport region 26 may include a compoundrepresented by Formula 601.[Ar₆₀₁]_(xe11)-[(L₆₀₁)_(xe1)-R₆₀₁]_(xe21)  Formula 601

In Formula 601,

Ar₆₀₁ may be a substituted or unsubstituted C₅-C₆₀ carbocyclic group, ora substituted or unsubstituted C₁-C₆₀ heterocyclic group;

xe11 may be 1, 2, or 3;

L₆₀₁ may be selected from a substituted or unsubstituted C₃-C₁₀cycloalkylene group, a substituted or unsubstituted C₁-C₁₀heterocycloalkylene group, a substituted or unsubstituted C₃-C₁₀cycloalkenylene group, a substituted or unsubstituted C₁-C₁₀heterocycloalkenylene group, a substituted or unsubstituted C₆-C₆₀arylene group, a substituted or unsubstituted C₁-C₆₀ heteroarylenegroup, a substituted or unsubstituted divalent non-aromatic condensedpolycyclic group, and a substituted or unsubstituted divalentnon-aromatic condensed heteropolycyclic group;

xe1 may be an integer selected from 0 to 5;

R₆₀₁ may be selected from a substituted or unsubstituted C₃-C₁₀cycloalkyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkylgroup, a substituted or unsubstituted C₃-C₁₀ cycloalkenyl group, asubstituted or unsubstituted C₁-C₁₀ heterocycloalkenyl group, asubstituted or unsubstituted C₆-C₆₀ aryl group, a substituted orunsubstituted C₆-C₆₀ aryloxy group, a substituted or unsubstitutedC₆-C₆₀ arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroarylgroup, a substituted or unsubstituted monovalent non-aromatic condensedpolycyclic group, a substituted or unsubstituted monovalent non-aromaticcondensed heteropolycyclic group, —Si(Q₆₀₁)(Q₆₀₂)(Q₆₀₃), —C(═O)(Q₆₀₁),—S(═O)₂(Q₆₀₁), and —P(═O)(Q₆₀₁)(Q₆₀₂);

Q₆₀₁ to Q₆₀₃ may be each independently a C₁-C₁₀ alkyl group, a C₁-C₁₀alkoxy group, a phenyl group, a biphenyl group, a terphenyl group, or anaphthyl group; and

xe21 may be an integer selected from 1 to 5.

In some embodiments, at least one of Ar₆₀₁(s) in the number of xe11 andR₆₀₁(s) in the number of xe21 may include such a π electron-depletednitrogen-containing ring as described above.

In some embodiments, in Formula 601, Ar₆₀₁ as a ring may be selectedfrom:

a benzene group, a naphthalene group, a fluorene group, aspiro-bifluorene group, a benzofluorene group, a dibenzofluorene group,a phenalene group, a phenanthrene group, an anthracene group, afluoranthene group, a triphenylene group, a pyrene group, a chrysenegroup, a naphthacene group, a picene group, a perylene group, apentaphene group, an indenoanthracene group, a dibenzofuran group, adibenzothiophene group, a carbazole group, an imidazole group, apyrazole group, a thiazole group, an isothiazole group, an oxazolegroup, an isoxazole group, a pyridine group, a pyrazine group, apyrimidine group, a pyridazine group, an indazole group, a purine group,a quinoline group, an isoquinoline group, a benzoquinoline group, aphthalazine group, a naphthyridine group, a quinoxaline group, aquinazoline group, a cinnoline group, a phenanthridine group, anacridine group, a phenanthroline group, a phenazine group, abenzimidazole group, an isobenzothiazole group, a benzoxazole group, anisobenzoxazole group, a triazole group, a tetrazole group, an oxadiazolegroup, a triazine group, a thiadiazole group, an imidazopyridine group,an imidazopyrimidine group and an azacarbazole group, and

a benzene group, a naphthalene group, a fluorene group, aspiro-bifluorene group, a benzofluorene group, a dibenzofluorene group,a phenalene group, a phenanthrene group, an anthracene group, afluoranthene group, a triphenylene group, a pyrene group, a chrysenegroup, a naphthacene group, a picene group, a perylene group, apentaphene group, an indenoanthracene group, a dibenzofuran group, adibenzothiophene group, a carbazole group, an imidazole group, apyrazole group, a thiazole group, an isothiazole group, an oxazolegroup, an isoxazole group, a pyridine group, a pyrazine group, apyrimidine group, a pyridazine group, an indazole group, a purine group,a quinoline group, an isoquinoline group, a benzoquinoline group, aphthalazine group, naphthyridine group, a quinoxaline group, aquinazoline group, a cinnoline group, a phenanthridine group, anacridine group, a phenanthroline group, a phenazine group, abenzimidazole group, an isobenzothiazole group, a benzoxazole group, anisobenzoxazole group, a triazole group, a tetrazole group, an oxadiazolegroup, a triazine group, a thiadiazole group, an imidazopyridine group,an imidazopyrimidine group, and an azacarbazole group, each substitutedwith at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxylgroup, a cyano group, a nitro group, an amidino group, a hydrazinogroup, a hydrazono group, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, aphenyl group, a biphenyl group, a terphenyl group, a naphthyl group,—Si(Q₃₁)(Q₃₂)(Q₃₃), —S(═O)₂(Q₃₁), and —P(═O)(Q₃₁)(Q₃₂); and

Q₃₁ to Q₃₃ may be each independently selected from a C₁-C₁₀ alkyl group,a C₁-C₁₀ alkoxy group, a phenyl group, a biphenyl group, a terphenylgroup, and a naphthyl group.

In Formula 601, when xe11 is 2 or greater, the at least two Ar₆₀₁(s) maybe linked to one another via a single bond.

In some other embodiments, in Formula 601, Ar₆₀₁ may be an anthracenegroup.

The buffer layer, the hole blocking layer, and/or the electron controllayer may each independently have a thickness of about 20 Å to about1000 Å, for example, about 30 Å to about 300 Å. When the thicknesses ofthe buffer layer, the hole blocking layer, and/or the electron controllayer are within these ranges, improved hole blocking characteristics orelectron control characteristics may be obtained without a substantialincrease in driving voltage.

The electron transport layer 26 may have a thickness of about 100 Å toabout 1000 Å, for example, about 150 Å to about 500 Å. When thethickness of the electron transport layer 26 is within these ranges,satisfactory or suitable electron transport characteristics may beobtained without a substantial increase in driving voltage.

The electron transport region 26 (for example, the electron transportlayer of the electron transport region 26) may further include ametal-containing material, in addition to the above-described materials.

The metal-containing material may include at least one selected from analkaline metal complex and an alkaline earth metal complex. A metal ionof the alkaline metal complex may be selected from a Li ion, a Na ion, aK ion, an Rb ion, and a Cs ion. A metal ion of the alkaline earth metalcomplex may be selected from a Be ion, a Mg ion, a Ca ion, a Sr ion, anda Ba ion. Ligands respectively coordinated to the metal ions of thealkaline metal complex and the alkaline earth metal complex may be eachindependently selected from a hydroxyquinoline, a hydroxyisoquinoline, ahydroxybenzoquinoline, a hydroxyacridine, a hydroxyphenanthridine, ahydroxyphenyloxazole, a hydroxyphenylthiazole, ahydroxydiphenyloxadiazole, a hydroxydiphenylthiadiazole, ahydroxyphenylpyridine, a hydroxyphenylbenzimidazole, ahydroxyphenylbenzothiazole, a bipyridine, a phenanthroline, and acyclopentadiene. However, the present disclosure is not limited thereto.

For example, the metal-containing material may include a Li complex. TheLi complex may include, for example, compound ET-D1 (lithium quinolate,LiQ) or compound ET-D2.

The electron transport region 26 may include an electron injection layerthat may facilitate injection of electrons from the cathode. Theelectron injection layer may directly contact the cathode.

The electron injection layer may have i) a single-layer structureincluding a single layer including a single material, ii) a single-layerstructure including a single layer including a plurality of differentmaterials, or iii) a multi-layer structure including a plurality oflayers including different materials.

The electron injection layer may include an alkaline metal, an alkalineearth metal, a rare earth metal, an alkaline metal compound, an alkalineearth metal compound, a rare earth metal compound, an alkaline metalcomplex, an alkaline earth metal complex, a rare earth metal complex, orany combination thereof.

The alkaline metal may be selected from Li, Na, K, Rb, and Cs. In someembodiments, the alkaline metal may be Li, Na, or Cs. In some otherembodiments, the alkaline metal may be Li or Cs. However, the presentdisclosure is not limited thereto.

The alkaline earth metal may be selected from Mg, Ca, Sr, and Ba.

The rare earth metal may be selected from Sc, Y, Ce, Tb, Yb, Gd, and Tb.

The alkaline metal compound, the alkaline earth metal compound, and therare earth metal compound may be selected from oxides and halides (forexample, fluorides, chlorides, bromides, iodides, and the like) of thealkaline metal, the alkaline earth metal, and the rare earth metal.

The alkaline metal compound may be selected from alkaline metal oxidessuch as Li₂O, Cs₂O, K₂O, and the like, and alkaline metal halides suchas LiF, NaF, CsF, KF, LiI, NaI, CsI, KI, RbI, and the like. In someembodiments, the alkaline metal compound may be selected from LiF, Li₂O,NaF, LiI, NaI, CsI, and KI. However, the present disclosure is notlimited thereto.

The alkaline earth metal compound may be selected from alkaline earthmetal compounds such as BaO, SrO, CaO, Ba_(x)Sr_(1-x)O (where 0<x<1),Ba_(x)Ca_(1-x)O (where 0<x<1), and the like. In some embodiments, thealkaline earth metal compound may be selected from BaO, SrO, and CaO.However, the present disclosure is not limited thereto.

The rare earth metal compound may be selected from YbF₃, ScF₃, ScO₃,Y₂O₃, Ce₂O₃, GdF₃, and TbF₃. In some embodiments, the rare earth metalcompound may be selected from YbF₃, ScF₃, TbF₃, YbI₃, ScI₃, and TbI₃.However, the present disclosure is not limited thereto.

The alkaline metal complex, the alkaline earth metal complex, and therare earth metal complex may include ions of the above-describedalkaline metals, alkaline earth metals, and rare earth metals. Ligandsrespectively coordinated to the metal ions of the alkaline metalcomplex, the alkaline earth metal complex, and the rare earth metalcomplex may be each independently selected from a hydroxyquinoline, ahydroxyisoquinoline, a hydroxybenzoquinoline, a hydroxyacridine, ahydroxyphenanthridine, a hydroxyphenyloxazole, a hydroxyphenylthiazole,a hydroxydiphenyloxadiazole, a hydroxydiphenylthiadiazole, ahydroxyphenylpyridine, a hydroxyphenylbenzimidazole, ahydroxyphenylbenzothiazole, a bipyridine, a phenanthroline, and acyclopentadiene. However, the present disclosure is not limited thereto.

In some embodiments, the electron injection layer may include only suchalkaline metals, alkaline earth metals, rare earth metals, alkalinemetal compounds, alkaline earth metal compounds, rare earth metalcompounds, alkaline metal complexes, alkaline earth metal complexes,rare earth metal complexes, or any combinations thereof as describedabove, or may further include such an organic material as listed abovein connection with the electron transport region 26. When the electroninjection layer further includes an organic material, the alkalinemetal, alkaline earth metal, rare earth metal, alkaline metal compound,alkaline earth metal compound, rare earth metal compound, alkaline metalcomplex, alkaline earth metal complex, rare earth metal complex, or anycombination thereof may be homogeneously or non-homogeneously (e.g.,heterogeneously) dispersed in a matrix of the organic material.

The electron injection layer may have a thickness of about 1 Å to about100 Å, for example, about 3 Å to about 90 Å. When the thickness of theelectron injection layer is within these ranges, satisfactory orsuitable electron injection characteristics may be obtained without asubstantial increase in driving voltage.

Second Electrode 27

When the second electrode 27 is a cathode serving as an electroninjection electrode, a material of the second electrode 27 may include ametal having a low work function, an alloy, an electrically conductivecompound, or any combinations thereof. When the second electrode 27 isan anode, a material of the second electrode 27 to facilitate holeinjection may be selected from materials having a high work function.

A material of the second electrode 27 may be selected from indium tinoxide (ITO), indium zinc oxide (IZO), tin oxide (SnO₂), zinc oxide(ZnO), zinc tin oxide (ZTO), copper indium oxide (CIO), copper zincoxide (CZO), gallium zinc oxide (GZO), aluminum zinc oxide (AZO), andany combinations thereof. However, the present disclosure is not limitedthereto. In some other embodiments, to form a semi-transmissiveelectrode or reflective electrode as the second electrode 27, a materialof the second electrode 27 may be selected from lithium (Li), magnesium(Mg), silver (Ag), aluminum (Al), aluminum-lithium (Al—Li), calcium(Ca), magnesium-indium (Mg—In), magnesium-silver (Mg—Ag), ytterbium(Yb), and any combinations thereof. However, the present disclosure isnot limited thereto. In some other embodiments, the second electrode 27may include graphene, carbon nanotube, or a conductive polymer such aspoly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS).However, the present disclosure is not limited thereto.

The second electrode 27 may have a single-layer structure or amulti-layer structure including a plurality of layers.

General Definition of Substituents

As used herein, the term “C₁-C₂₀ alkyl group” refers to a linear orbranched aliphatic hydrocarbon monovalent group having 1 to 20 carbonatoms. Non-limiting examples of the C₁-C₂₀ alkyl group include a methylgroup, an ethyl group, a propyl group, an isobutyl group, a sec-butylgroup, a tert-butyl group, a pentyl group, an iso-amyl group, and ahexyl group. As used herein, the term “C₁-C₂₀ alkylene group” refers toa divalent group having substantially the same structure as the C₁-C₂₀alkyl group, except that the C₁-C₂₀ alkylene group is divalent insteadof monovalent.

As used herein, the term “C₁-C₂₀ alkoxy group” refers to a monovalentgroup represented by —OA₁₀₁ (where A₁₀₁ is a C₁-C₂₀ alkyl group asdescribed above). Non-limiting examples of the C₁-C₂₀ alkoxy groupinclude a methoxy group, an ethoxy group, and an isopropyloxy group.

As used herein, the term “C₃-C₁₀ cycloalkyl group” refers to amonovalent, monocyclic saturated hydrocarbon group having 3 to 10 carbonatoms. Non-limiting examples of the C₃-C₁₀ cycloalkyl group include acyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexylgroup, and a cycloheptyl group. As used herein, the term “C₃-C₁₀cycloalkylene group” refers to a divalent group having substantially thesame structure as the C₃-C₁₀ cycloalkyl group, except that the C₃-C₁₀cycloalkylene group is divalent instead of monovalent.

As used herein, the term “C₁-C₁₀ heterocycloalkyl group” refers to amonovalent monocyclic group having 1 to 10 carbon atoms in which atleast one heteroatom selected from N, O, Si, P, and S is included as aring-forming atom. Non-limiting examples of the C₁-C₁₀ heterocycloalkylgroup include a 1,2,3,4-oxatriazolidinyl group, a tetrahydrofuranylgroup, and a tetrahydrothiophenyl group.

As used herein, the term “C₃-C₁₀ cycloalkenyl group” refers to amonovalent monocyclic group having 3 to 10 carbon atoms that includes atleast one double bond in the ring but does not have aromaticity (e.g.,the C₃-C₁₀ cycloalkenyl group or a ring of the C₃-C₁₀ cycloalkenyl groupis not aromatic). Non-limiting examples of the C₃-C₁₀ cycloalkenyl groupinclude a cyclopentenyl group, a cyclohexenyl group, and a cycloheptenylgroup. As used herein, the term “C₃-C₁₀ cycloalkenylene group” refers toa divalent group having substantially the same structure as the C₃-C₁₀cycloalkenyl group, except that the C₃-C₁₀ cycloalkenylene group isdivalent instead of monovalent.

As used herein, the term “C₁-C₁₀ heterocycloalkenyl group” refers to amonovalent monocyclic group having 1 to 10 carbon atoms that includes atleast one double bond in the ring and in which at least one heteroatomselected from N, O, Si, P, and S is included as a ring-forming atom.Non-limiting examples of the C₁-C₁₀ heterocycloalkenyl group include a4,5-dihydro-1,2,3,4-oxatriazole group, a 2,3-dihydrofuranyl group, and a2,3-dihydrothiophenyl group.

As used herein, the term “C₆-C₆₀ aryl group” refers to a monovalent,aromatic carbocyclic group having 6 to 60 carbon atoms, and a C₆-C₆₀arylene group refers to a divalent, aromatic carbocyclic group having 6to 60 carbon atoms. Non-limiting examples of the C₆-C₆₀ aryl groupinclude a phenyl group, a naphthyl group, an anthracenyl group, aphenanthrenyl group, a pyrenyl group, and a chrysenyl group. When theC₆-C₆₀ aryl group and the C₆-C₆₀ arylene group include at least tworings, the rings may be condensed to each other (e.g., fused together).

As used herein, the term “C₁-C₆₀ heteroaryl group” refers to amonovalent, aromatic heterocyclic group having 1 to 60 carbon atoms inwhich at least one heteroatom selected from N, O, Si, P, and S isincluded as a ring-forming atom. Non-limiting examples of the C₁-C₆₀heteroaryl group include a pyridinyl group, a pyrimidinyl group, apyrazinyl group, a pyridazinyl group, a triazinyl group, a quinolinylgroup, and an isoquinolinyl group. When the C₁-C₆₀ heteroaryl groupincludes at least two rings, the rings may be condensed to each other(e.g., fused together).

As used herein, the term “C₆-C₆₀ aryloxy group” indicates —OA₁₀₂ (whereA₁₀₂ is a C₆-C₆₀ aryl group as described above), and a C₆-C₆₀ arylthiogroup indicates —SA₁₀₃ (where A₁₀₃ is a C₆-C₆₀ aryl group as describedabove).

As used herein, the term “monovalent non-aromatic condensed polycyclicgroup” refers to a monovalent group having at least two rings condensedto each other (e.g., fused together), in which only carbon atoms (forexample, 8 to 60 carbon atoms) are exclusively included as ring-formingatoms and the entire molecule has non-aromaticity (e.g., the entiremonovalent non-aromatic condensed polycyclic group is not aromatic). Anon-limiting example of the monovalent non-aromatic condensed polycyclicgroup includes a fluorenyl group. As used herein, the term “divalentnon-aromatic condensed polycyclic group” refers to a divalent grouphaving substantially the same structure as the monovalent non-aromaticcondensed polycyclic group, except that the divalent non-aromaticcondensed polycyclic group is divalent instead of monovalent.

As used herein, the term “monovalent non-aromatic condensedheteropolycyclic group” refers to a monovalent group having at least tworings condensed to each other (e.g., fused together), in which carbonatoms (for example, 1 to 60 carbon atoms) and at least one heteroatomselected from N, O, Si, P, and S are ring-forming atoms and the entiremolecule has non-aromaticity (e.g., the entire monovalent non-aromaticcondensed heteropolycyclic group is not aromatic). A non-limitingexample of the monovalent non-aromatic condensed heteropolycyclic groupincludes a carbazolyl group. As used herein, the term “divalentnon-aromatic condensed heteropolycyclic group” refers to a divalentgroup having substantially the same structure as the monovalentnon-aromatic condensed heteropolycyclic group, except that the divalentnon-aromatic condensed heteropolycyclic group is divalent instead ofmonovalent.

As used herein, the term “C₅-C₆₀ carbocyclic group” refers to amonocyclic or polycyclic group including carbon atoms (for example, 5 to60 carbon atoms) that are exclusively included as ring-forming atoms.The C₅-C₆₀ carbocyclic group may be an aromatic carbocyclic group or anon-aromatic carbocyclic group. The C₅-C₆₀ carbocyclic group may be aring such as a benzene, a monovalent group such as a phenyl group, or adivalent group such as a phenylene group. In some embodiments, theC₅-C₆₀ carbocyclic group may be a trivalent group or a tetravalent groupdepending on the number of substituents linked thereto. However,examples of the C₅-C₆₀ carbocyclic group are not limited thereto.

As used herein, the term “C₁-C₆₀ heterocyclic group” refers to a grouphaving substantially the same structure as the above-described C₅-C₆₀carbocyclic group, but in which carbon atoms (for example, 1 to 60carbon atoms) and at least one heteroatom selected from N, O, Si, P andS are included as ring-forming atoms.

As used herein, at least one selected from substituents of thesubstituted C₅-C₆₀ carbocyclic group, the substituted C₁-C₆₀heterocyclic group, the substituted C₃-C₁₀ cycloalkylene group, thesubstituted C₁-C₁₀ heterocycloalkylene group, the substituted C₃-C₁₀cycloalkenylene group, the substituted C₁-C₁₀ heterocycloalkenylenegroup, the substituted C₆-C₆₀ arylene group, the substituted C₁-C₆₀heteroarylene group, the substituted divalent non-aromatic condensedpolycyclic group, the substituted divalent non-aromatic condensedheteropolycyclic group, the substituted C₁-C₆₀ alkyl group, thesubstituted C₂-C₆₀ alkenyl group, the substituted C₂-C₆₀ alkynyl group,the substituted C₁-C₆₀ alkoxy group, the substituted C₃-C₁₀ cycloalkylgroup, the substituted C₁-C₁₀ heterocycloalkyl group, the substitutedC₃-C₁₀ cycloalkenyl group, the substituted C₁-C₁₀ heterocycloalkenylgroup, the substituted C₆-C₆₀ aryl group, the substituted C₆-C₆₀ aryloxygroup, the substituted C₆-C₆₀ arylthio group, the substituted C₁-C₆₀heteroaryl group, the substituted monovalent non-aromatic condensedpolycyclic group, and the substituted monovalent non-aromatic condensedheteropolycyclic group may be selected from:

deuterium(-D), —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, anitro group, an amidino group, a hydrazino group, a hydrazono group, aC₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl group, anda C₁-C₆₀ alkoxy group,

a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl group,and a C₁-C₆₀ alkoxy group, each substituted with at least one selectedfrom deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, anitro group, an amidino group, a hydrazino group, a hydrazono group, aC₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ arylgroup, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀heteroaryl group, a monovalent non-aromatic condensed polycyclic group,a monovalent non-aromatic condensed heteropolycyclic group,—Si(C₂₁₁)(C₂₁₂)(Q₁₃), —N(Q₁₁)(Q₁₂), —B(Q₁₁)(Q₁₂), —C(═O)(Q₁₁),—S(═O)₂(Q₁₁), and —P(═O)(Q₁₁)(Q₁₂),

a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ arylgroup, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀heteroaryl group, a monovalent non-aromatic condensed polycyclic group,and a monovalent non-aromatic condensed heteropolycyclic group,

a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ arylgroup, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀heteroaryl group, a monovalent non-aromatic condensed polycyclic group,and a monovalent non-aromatic condensed heteropolycyclic group, eachsubstituted with at least one selected from deuterium, —F, —Cl, —Br, —I,a hydroxyl group, a cyano group, a nitro group, an amidino group, ahydrazino group, a hydrazono group, a C₁-C₆₀ alkyl group, a C₂-C₆₀alkenyl group, a C₂-C₆₀ alkynyl group, a C₁-C₆₀ alkoxy group, a C₃-C₁₀cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenylgroup, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl group, amonovalent non-aromatic condensed polycyclic group, a monovalentnon-aromatic condensed heteropolycyclic group, —Si(Q₂₁)(Q₂₂)(Q₂₃),—N(Q₂₁)(Q₂₂), —B(Q₂₁)(Q₂₂), —C(═O)(Q₂₁), —S(═O)₂(Q₂₁), and—P(═O)(Q₂₁)(Q₂₂), and

—Si(Q₃₁)(Q₃₂)(Q₃₃), —N(Q₃₁)(Q₃₂), —B(Q₃₁)(Q₃₂), —C(═O)(Q₃₁),—S(═O)₂(Q₃₁), and —P(═O)(Q₃₁)(Q₃₂); and

Q₁₁ to Q₁₃, Q₂₁ to Q₂₃, and Q₃₁ to Q₃₃ may be each independentlyselected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, acyano group, a nitro group, an amidino group, a hydrazino group, ahydrazono group, a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀alkynyl group, a C₁-C₆₀ alkoxy group, a C₃-C₁₀ cycloalkyl group, aC₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₁-C₆₀ heteroarylgroup, a monovalent non-aromatic condensed polycyclic group, amonovalent non-aromatic condensed heteropolycyclic group, a biphenylgroup, and a terphenyl group.

As used herein, the term “biphenyl group” refers to a “phenyl groupsubstituted with a phenyl group.” The “biphenyl group” may be a“substituted phenyl group” having a substituent which is a “C₆-C₆₀ arylgroup.”

As used herein, the term “terphenyl group” refers to a “phenyl groupsubstituted with a biphenyl group.” The “terphenyl group” may be a“substituted phenyl group” having a substituent which is a C₆-C₆₀ arylgroup substituted with a C₆-C₆₀ aryl group.

As used herein, * and *′ indicate, unless defined otherwise, a bindingsite to an adjacent atom in the corresponding formula.

One or more embodiments of light-emitting devices according to thepresent disclosure will now be described in more detail with referenceto the following examples. However, these examples are only forillustrative purposes and are not intended to limit the scope of the oneor more embodiments of the present disclosure.

EXAMPLE

A 15 Ω/cm² ITO glass substrate (having a thickness of 1200 Å, availablefrom Corning Inc.) was cut to a size of 50 mm×50 mm×0.7 mm and thensonicated in isopropyl alcohol and deionized water each for fiveminutes, and then cleaned by irradiation with ultraviolet rays for 30minutes and exposure to ozone. The resulting glass substrate with an ITOanode thereon was mounted into a vacuum deposition device.

2-TNATA was vacuum-deposited on the ITO anode of the glass substrate toform a hole injection layer having a thickness of about 600 Å, and NPBwas then vacuum-deposited on the HIL to form a hole transport layerhaving a thickness of about 300 Å, thereby forming a hole transportregion.

An emission layer was then formed on the hole transport region, whereinthe emission layer included quantum dots having a core-shell structureincluding CdSe in the core and ZnS in the shell.

After FeF₂ was deposited on the emission layer to form an inorganiclayer having a thickness of about 400 Å, Al was vacuum-deposited on theinorganic layer to form a cathode having a thickness of about 1000 Å,thereby manufacturing a light-emitting device. Equipment used in thedeposition processes included a Suicel plus 200 system (available fromSunic System Ltd.)

Comparative Examples 1 and 2

Light-emitting devices were manufactured in the same manner as describedwith respect to Example 1, except that ZnO (Comparative Example 1) andZnS (Comparative Example 2) were used, instead of FeF₂, to form theinorganic layer.

TABLE 1 Emission Inorganic Driving Efficiency Color T95 Example layerlayer [V] [cd/A] CIE x CIE y [hr @100 mA/cm²] Example 1 CdSe/ZnS FeF₂ 380 0.67 0.33 50000 Comparative Example 1 CdSe/ZnS ZnO 3.5 40 0.65 0.3110000 Comparative Example 2 CdSe/ZnS ZnS 3.2 15 0.63 0.35 80

Referring to Table 1, the light-emitting device of Example 1 was foundto have improved driving voltage, efficiency, and half lifetime,compared to those of the light-emitting devices of Comparative Examples1 and 2.

When an inorganic layer of an light-emitting device is formed of ZnO,which is a material used in inorganic layers, by a solution process(spin coating and the like), as in Comparative Example 1, the inorganiclayer may undergo stability degradation over time, leading to reduceddevice reproducibility in manufacturing processes. In addition, oxygenoutgassing caused from the thermal decomposition of ZnO may lower alevel of vacuum (e.g., a level of vacuum of a chamber used formanufacturing the device) and hinder deposition.

However, in a light-emitting device according to an embodiment of thepresent disclosure, which may include an inorganic layer formed of ametal halide, for example, FeF₂ as used in Example 1, and an emissionlayer including quantum dots, the energy level of the metal halide maybe appropriate or suitable for the emission layer including quantum dotsand the melting point thereof may also be low to facilitate thermaldeposition, so that it may be easier to ensure reliability andreproducibility of devices according to embodiments of the presentdisclosure, as compared to a light-emitting device including aninorganic layer using another material (e.g., ZnO).

As described above, according to the one or more embodiments, a quantumdot light-emitting device may have long lifespan, high reliability, andhigh reproducibility.

Spatially relative terms, such as “beneath,” “below,” “lower,” “under,”“above,” “upper,” and the like, may be used herein for ease ofexplanation to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. It will beunderstood that the spatially relative terms are intended to encompassdifferent orientations of the device in use or in operation, in additionto the orientation depicted in the figures. For example, if the devicein the figures is turned over, elements described as “below” or“beneath” or “under” other elements or features would then be oriented“above” the other elements or features. Thus, the example terms “below”and “under” can encompass both an orientation of above and below. Thedevice may be otherwise oriented (e.g., rotated 90 degrees or at otherorientations) and the spatially relative descriptors used herein shouldbe interpreted accordingly.

It will be understood that when an element or layer is referred toherein as being “on,” “connected to,” or “coupled to” another element orlayer, it can be directly on, connected to, or coupled to the otherelement or layer, or one or more intervening elements or layers may bepresent. In addition, it will also be understood that when an element orlayer is referred to as being “between” two elements or layers, it canbe the only element or layer between the two elements or layers, or oneor more intervening elements or layers may also be present.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentdisclosure. As used herein, the singular forms “a” and “an” are intendedto include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes,” and “including,” when used inthis specification, specify the presence of the stated features,integers, acts, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,integers, acts, operations, elements, components, and/or groups thereof.

As used herein, the terms “substantially,” “about,” and similar termsare used as terms of approximation and not as terms of degree, and areintended to account for the inherent deviations in measured orcalculated values that would be recognized by those of ordinary skill inthe art. Further, the use of “may” when describing embodiments of thepresent disclosure refers to “one or more embodiments of the presentdisclosure.” As used herein, the terms “use,” “using,” and “used” may beconsidered synonymous with the terms “utilize,” “utilizing,” and“utilized,” respectively. Also, the term “exemplary” is intended torefer to an example or illustration.

Also, any numerical range recited herein is intended to include allsub-ranges of the same numerical precision subsumed within the recitedrange. For example, a range of “1.0 to 10.0” is intended to include allsubranges between (and including) the recited minimum value of 1.0 andthe recited maximum value of 10.0, that is, having a minimum value equalto or greater than 1.0 and a maximum value equal to or less than 10.0,such as, for example, 2.4 to 7.6. Any maximum numerical limitationrecited herein is intended to include all lower numerical limitationssubsumed therein, and any minimum numerical limitation recited in thisspecification is intended to include all higher numerical limitationssubsumed therein. Accordingly, Applicant reserves the right to amendthis specification, including the claims, to expressly recite anysub-range subsumed within the ranges expressly recited herein.

It should be understood that embodiments described herein should beconsidered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments.

While one or more embodiments have been described with reference to thefigures, it will be understood by those of ordinary skill in the artthat various changes in form and details may be made therein withoutdeparting from the spirit and scope of the present disclosure as definedby the following claims, and equivalents thereof.

What is claimed is:
 1. A light-emitting device comprising: a firstelectrode; a second electrode opposite to the first electrode; anemission layer between the first electrode and the second electrode, theemission layer comprising quantum dots; a hole transport region betweenthe first electrode and the emission layer; and an inorganic layerbetween the emission layer and the second electrode, the inorganic layercomprising a metal halide, wherein the metal halide comprises analkaline earth metal halide, a transition metal halide, apost-transition metal halide, or any combination thereof, wherein anenergy band gap of the inorganic layer is about 3.1 eV to about 4.6 eV,and the quantum dots have a core-shell structure comprising a corecomprising a first semiconductor crystal and a shell comprising a secondsemiconductor crystal.
 2. The light-emitting device of claim 1, whereinthe inorganic layer further comprises a trivalent metal ion.
 3. Thelight-emitting device of claim 1, wherein the metal halide comprises asilver (Ag) halide, a cadmium (Cd) halide, a mercury (Hg) halide, amanganese (Mn) halide, an iron (Fe) halide, a cobalt (Co) halide, anickel (Ni) halide, a copper (Cu) halide, a zinc (Zn) halide, or anycombination thereof.
 4. The light-emitting device of claim 1, wherein athickness of the inorganic layer is 200 to 1000 Å.
 5. The light-emittingdevice of claim 1, wherein a first semiconductor of the firstsemiconductor crystal and a second semiconductor of the secondsemiconductor crystal each independently comprise a compound including aGroup 12 element and a Group 16 element, a compound including a Group 13element and a Group 15 element, a compound including a Group 14 elementand a Group 16 element, or any combination thereof.
 6. Thelight-emitting device of claim 1, wherein a first semiconductor of thefirst semiconductor crystal and a second semiconductor of the secondsemiconductor crystal each independently comprise CdS, CdSe, CdTe, ZnS,ZnSe, ZnTe, HgS, HgSe, HgTe, CdSTe, GaP, GaAs, GaSb, InP InAs, InSb,PbS, PbSe, PbTe, or any combination thereof.
 7. The light-emittingdevice of claim 1, wherein a second semiconductor of the secondsemiconductor crystal has an energy band gap equal to or greater than anenergy band gap of a first semiconductor of the first semiconductorcrystal.
 8. The light-emitting device of claim 1, wherein the holetransport region includes metal oxide nanoparticles, and the metal oxidenanoparticles include at least one selected from NiO, MoO₃, Cr₂O₃,Bi₂O₃, a p-type ZnO, and a p-type GaN.
 9. The light-emitting device ofclaim 1, wherein the hole transport region includes an organic compoundand the organic compound includes at least one selected from m-MTDATA,TDATA, 2-TNATA, NPB(NPD), β-NPB, TPD, Spiro-TPD, Spiro-NPB, methylatedNPB, TAPC, HMTPD, 4,4′,4″-tris(N-carbazolyl)triphenylamine (TCTA),polyaniline/dodecylbenzene sulfonic acid (Pani/DBSA),poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS),polyaniline/camphor sulfonic acid (Pani/CSA), polyaniline/poly(4-styrenesulfonate) (PANI/PSS), a compound represented by Formula 201, and acompound represented by Formula 202:

in formulae 201 and 202, L₂₀₁ to L₂₀₄ is each independently selectedfrom a substituted or unsubstituted C₃-C₁₀ cycloalkylene group, asubstituted or unsubstituted heterocycloalkylene group, a substituted orunsubstituted C₃-C₁₀ cycloalkenylene group, a substituted orunsubstituted heterocycloalkenylene group, a substituted orunsubstituted C₆-C₆₀ arylene group, a substituted or unsubstitutedC₁-C₆₀ heteroarylene group, a substituted or unsubstituted divalentnon-aromatic condensed polycyclic group, and a substituted orunsubstituted divalent non-aromatic condensed heteropolycyclic group;L₂₀₅ is selected from *—O—*′, *—S—*′, *—N(Q₂₀₁)-*′, a substituted orunsubstituted C₁-C₂₀ alkylene group, a substituted or unsubstitutedC₂-C₂₀ alkenylene group, a substituted or unsubstituted C₃-C₁₀cycloalkylene group, a substituted or unsubstituted C₁-C₁₀heterocycloalkylene group, a substituted or unsubstituted C₃-C₁₀cycloalkenylene group, a substituted or unsubstituted C₁-C₁₀heterocycloalkenylene group, a substituted or unsubstituted C₆-C₆₀arylene group, a substituted or unsubstituted C₁-C₆₀ heteroarylenegroup, a substituted or unsubstituted divalent non-aromatic condensedpolycyclic group, and a substituted or unsubstituted divalentnon-aromatic condensed heteropolycyclic group; xa1 to xa4 is eachindependently an integer selected from 0 to 3; xa5 is an integerselected from 1 to 10; and R₂₀₁ to R₂₀₄ and Q₂₀₁ is each independentlyselected from a substituted or unsubstituted C₃-C₁₀ cycloalkyl group, asubstituted or unsubstituted C₁-C₁₀ heterocycloalkyl group, asubstituted or unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted orunsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted orunsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted C₆-C₆₀aryloxy group, a substituted or unsubstituted C₆-C₆₀ arylthio group, asubstituted or unsubstituted C₁-C₆₀ heteroaryl group, a substituted orunsubstituted monovalent non-aromatic condensed polycyclic group, and asubstituted or unsubstituted monovalent non-aromatic condensedheteropolycyclic group.
 10. The light-emitting device of claim 1,wherein a thickness of the hole transport region is 100 to 1000 Å.
 11. Alight-emitting device comprising: a first electrode; a second electrodeopposite to the first electrode; an emission layer between the firstelectrode and the second electrode, the emission layer comprisingquantum dots; a hole transport region between the first electrode andthe emission layer; and an inorganic layer between the emission layerand the second electrode, the inorganic layer comprises a metal halide,wherein the metal halide comprises an alkaline earth metal halide, atransition metal halide, a post-transition metal halide, or anycombination thereof, and wherein the quantum dots have a core-shellstructure comprising a core comprising a first semiconductor crystal anda shell comprising a second semiconductor crystal.
 12. Thelight-emitting device of claim 11, wherein the metal halide comprises asilver (Ag) halide, a cadmium (Cd) halide, a mercury (Hg) halide, amanganese (Mn) halide, an iron (Fe) halide, a cobalt (Co) halide, anickel (Ni) halide, a copper (Cu) halide, a zinc (Zn) halide, or anycombination thereof.
 13. The light-emitting device of claim 11, whereina thickness of the inorganic layer is 200 to 1000 Å.
 14. Thelight-emitting device of claim 11, wherein a first semiconductor of thefirst semiconductor crystal and a second semiconductor of the secondsemiconductor crystal each independently comprise a compound including aGroup 12 element and a Group 16 element, a compound including a Group 13element and a Group 15 element, a compound including a Group 14 elementand a Group 16 element, or any combination thereof.
 15. Thelight-emitting device of claim 11, wherein a first semiconductor of thefirst semiconductor crystal and a second semiconductor of the secondsemiconductor crystal each independently comprise CdS, CdSe, CdTe, ZnS,ZnSe, ZnTe, HgS, HgSe, HgTe, CdSTe, GaP, GaAs, GaSb, InP InAs, InSb,PbS, PbSe, PbTe, or any combination thereof.
 16. The light-emittingdevice of claim 11, wherein a second semiconductor of the secondsemiconductor crystal has an energy band gap equal to or greater than anenergy band gap of a first semiconductor of the first semiconductorcrystal.
 17. The light-emitting device of claim 11, wherein the holetransport region includes metal oxide nanoparticles, and the metal oxidenanoparticles include at least one selected from NiO, MoO₃, Cr₂O₃,Bi₂O₃, a p-type ZnO, and a p-type GaN.
 18. The light-emitting device ofclaim 11, wherein the hole transport region includes an organic compoundand the organic compound includes at least one selected from m-MTDATA,TDATA, 2-TNATA, NPB(NPD), β-NPB, TPD, Spiro-TPD, Spiro-NPB, methylatedNPB, TAPC, HMTPD, 4,4′,4″-tris(N-carbazolyl)triphenylamine (TCTA),polyaniline/dodecylbenzene sulfonic acid (Pani/DBSA),poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS),polyaniline/camphor sulfonic acid (Pani/CSA), polyaniline/poly(4-styrenesulfonate) (PANI/PSS), a compound represented by Formula 201, and acompound represented by Formula 202:

in formulae 201 and 202, L₂₀₁ to L₂₀₄ is each independently selectedfrom a substituted or unsubstituted C₃-C₁₀ cycloalkylene group, asubstituted or unsubstituted C₁-C₁₀ heterocycloalkylene group, asubstituted or unsubstituted C₃-C₁₀ cycloalkenylene group, a substitutedor unsubstituted C₁-C₁₀ heterocycloalkenylene group, a substituted orunsubstituted C₆-C₆₀ arylene group, a substituted or unsubstitutedC₁-C₆₀ heteroarylene group, a substituted or unsubstituted divalentnon-aromatic condensed polycyclic group, and a substituted orunsubstituted divalent non-aromatic condensed heteropolycyclic group;L₂₀₅ is selected from *—O—*′, *—S—*′, *—N(Q₂₀₁)-*′, a substituted orunsubstituted C₁-C₂₀ alkylene group, a substituted or unsubstitutedC₂-C₂₀ alkenylene group, a substituted or unsubstituted C₃-C₁₀cycloalkylene group, a substituted or unsubstituted C₁-C₁₀heterocycloalkylene group, a substituted or unsubstituted C₃-C₁₀cycloalkenylene group, a substituted or unsubstituted C₁-C₁₀heterocycloalkenylene group, a substituted or unsubstituted C₆-C₆₀arylene group, a substituted or unsubstituted C₁-C₆₀ heteroarylenegroup, a substituted or unsubstituted divalent non-aromatic condensedpolycyclic group, and a substituted or unsubstituted divalentnon-aromatic condensed heteropolycyclic group; xa1 to xa4 is eachindependently an integer selected from 0 to 3; xa5 is an integerselected from 1 to 10; and R₂₀₁ to R₂₀₄ and Q₂₀₁ is each independentlyselected from a substituted or unsubstituted C₃-C₁₀ cycloalkyl group, asubstituted or unsubstituted C₁-C₁₀ heterocycloalkyl group, asubstituted or unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted orunsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted orunsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted C₆-C₆₀aryloxy group, a substituted or unsubstituted C₆-C₆₀ arylthio group, asubstituted or unsubstituted C₁-C₆₀ heteroaryl group, a substituted orunsubstituted monovalent non-aromatic condensed polycyclic group, and asubstituted or unsubstituted monovalent non-aromatic condensedheteropolycyclic group.